This invention relates to collet and nut assemblies used in stud welders, and is more particularly concerned with reducing or eliminating the most commonly experienced failure modes associated with the collets.
A conventional stud welder uses a metal collet through which metal studs are advanced. As the stud advances in the collet, a leading stud flange forces a deflection in tangs of the collet, which flex to allow the flange to pass through. The force required to advance the flange of the stud through the collet is the feeding force. Once the flange passes through the collet, the tangs spring back, clamping down on the stud shank. After the stud has been welded to the workpiece, the shank can be pulled from the collet. The force required to pull the shank from the collet at this stage is the holding force.
U.S. Pat. No. 6,015,962 granted Jan. 18, 2000 (incorporated herein by reference) discloses a prior art collet used in a stud welder. The collet comprises, inter alia, a series of circumferentially spaced tangs separated by longitudinal slots, each of which has a relief hole at a root end remote from the tip end of the slot.